Solar Section Aims & Objectives


  • To promote every aspect of solar astronomy and to provide information and encouragement to members in relation to the study of the Sun.


  • Provide relevant and up-to-date information and advice in relation to the Section’s programme of work
  • Encourage the exchange of information and expertise between observers for mutual help
  • Promote solar study and observation for beginners
  • Circulate current solar observational information and data
  • Explore and develop modern techniques for both solar observation and data recording.

Solar Section Programme of Work

  • Observation of Naked-eye sunspots
  • Counts of Active Areas, the Relative Sunspot Numbers and the Quality Number
  • 152mm (6-inch) whole disk drawings and the detailed drawings of individual groups and sunspots
  • Observation of bright faculae in the sunspot zones and polar faculae
  • Imaging of the solar disk, individual groups and faculae
  • Observations and imaging in Hydrogen-alpha of prominences, filaments, plage and flares
  • Observations and imaging in Calcium K emission of active area features
  • Observations of solar emissions (effects of solar flares on terrestrial radio transmission and on the Earth’s magnetic field)
  • Monthly reporting of white light and narrow band observations

Notes on the above programme are provided:

1. For observing naked-eye spots a safe solar filter (such as Welders glass, shade 14, mylar film, or inconel filter) is a necessary. DO NOT USE ANY OTHER MATERIAL no matter how dark it appears. If in doubt about the safety of any solar filter contact the Director for advice before using it.

When a naked eye sunspot is seen, a note should be made of the date and time, whether the spot was seen easily or only just glimpsed, and on which part of the disk it appeared. It will then be easy to identify the spot from whole disk drawings. If two or more spots are seen near to one another, a brief note should be added to indicate their relative positions.

Naked-eye observations should precede any telescopic examination of the Sun as they are of no value statistically if the positions of the spot are known in advance.

2. Counts of Active Areas (AAs), the Relative Sunspot Number (R) and the Quality Number (Q) are made from either whole disk drawings, or directly from the Sun itself. Projection of the Sun’s disk onto a white card is probably the best method of use. Be especially careful to look out for any very small spots (usually called pores) on the disk as these can be easily overlooked. The notes below give the rules to be followed.

Active Areas (AAs)
Every sunspot, however small, counts as a separate Active Area if it is at least 10o of latitude or longitude from its nearest neighbour. The same rule applies to spot groups. A large group, however, spread out in longitude, is still one Active Area unless it has distinct separate centres of activity at least 10o apart.

From time to time distinct groups do break out nearer than 10o from each other. This is mostly in latitude which be in the order of 5o. When such groups occur they should be counted as two AAs and a note made that this has been done.

Relative Sunspot Number (R)
To find the Relative Sunspot Number proceed as above then count all the spots that you can see either singly or within groups. For the purpose of this exercise, the Relative Sunspot number = 10g + f. Therefore “g” represents your AAs and “f” the number of spots counted within your AAs. The final calculation that has to be made to get R is therefore to multiply “g” by 10 and then add “f”.

The monthly on-line report form is used to record both Active Areas and Relative Sunspot Number counts. In each observing day the number of AAs and the R is noted: non-observing days are left blank. If you wish only to record AAs, fill in the column marked “gn” (AAs in the northern hemisphere), “gs” (AAs in the southern hemisphere) and “g” (total Aas north and south), add them up at the end of each month and calculate your Mean Daily Frequency (MDF) by dividing the total by the number of observing days. If you cannot distinguish between north and south on the Sun’s disk just fill in “g”.

For R fill in the “gn”, “gs” and “g” columns on the monthly report form as before and then count all the spots that you can see either singly or in groups and put this total into the appropriate “fn”, “fs” and “f” columns. To fill in the R column multiply “g” by 10 and add to “f” to get R for each day. At the end of the observing month, calculate your monthly R by dividing the total of the R column by the total number of observing days that month.

Note: “gn” = AAs in the North; “gs” = AAs in the South; “g” = total AAs; “fn” = all spots counted in the North; “fs” = all spots counted in the South; and “f” = total number of spots counted. The completed form should be sent to the Director as soon as possible at the end of each month.

Quality Number (Q)
The Q Number is based on a value assigned to each group visible each day using the Zurich sunspot group classification.  So an A group has the value of 1, a B group 2 etc. with the more complex groups having a higher number.  For each daily observation, these numbers are added together to give a Q value for each day.  Further details can be found in the BAA paper ‘Analysing sunspot activity: A qualitative and quantitative approach’, Frank J. Ventura and Tony Tanti, J. Brit. Astron. Assoc., 98, 282-286 (1988).

3. Whole disk drawings showing the positions and types of spots should be made on the 152mm (6-inch) diameter solar blanks. On each sheet on which a drawing is made should be written the date and the time of observation (in UT), the type of telescope used and the method of observation, a brief note of the observing conditions, the rotation number and the values of Bo and Lo and P obtained, for example, from the BAA Handbook, and the observer’s name.

If possible, a series of drawings of complex spots or groups of spots should be made. These will show the course of growth and decline of the disturbances. Single drawings, however, will be useful as they can be associated with the drawings of other observers.

4. When conditions permit, the outlines of bright faculae should be shown on the drawings in addition to the spots or, better still, the faculae patches can be indicated with yellow pencil.

Polar faculae appear as bright points of light, a few seconds of arc in diameter, on the north and south polar caps usually above 60o latitude. They are not grouped so as to form luminous patches like the faculae found at lower latitudes, but are scattered at random. They are best observed in a darkened observatory by projection using an equivalent disk 250mm (10 inches) or more in diameter. Good seeing is essential.

5. Imaging of all white light features is encouraged as an excellent way of recording such features. There are a variety of techniques for white light imaging such as using DSLR camera, astronomical webcams or CCDs.

6. The distribution of prominences around the disk should be recorded as far as possible, their proportional sizes and latitudes, North and South being recorded separately. It is also useful to divide this count into prominences seen in the spot zone latitudes 0o – 40o, and those seen at the higher latitudes 40o to the poles. A total MDF is made at the end of the observing month in the same way as for AAs.

As with images/drawings of individual sunspot groups, a series of images/drawings of prominences showing their changes would be useful. Prominences usually appear pinkish red and should, if observed over a long enough period, be labelled as either active or quiescent. Filaments usually appear black or dark brown and are the same as prominences but seen against the Sun’s disk. These should be noted if they show any motions or activity, any sudden disappearances etc.

The positions, size and intensity of solar flares should be noted. It is important to accurately report the time of these events (so they can be corrected with other external data relating to flares).

7. Any features observed/imaged in Calcium K, such as those associated with sunspots groups, should be recorded.

8. In association with the BAA Radio Astronomy Group, Very Low Frequency (VLF) radio observations of solar flares can be obtained through changes in the Earth’s ionosphere called Sudden Ionospheric Disturbances. VLF equipment can be purchased via the UK Radio Astronomy Association (UKRAA). In addition measurements of the Earth’s magnetic field are also of interest to the Solar Section.

9. Monthly reporting of white light and hydrogen alpha solar features is encouraged as described in the section on Submitting Observation. Image should also be submitted for possible inclusion in the monthly newsletter and in the Journal.

Revised June 2018.

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